Comparison of electromyographic activity in the lumbar paraspinal muscles of subjects with and without chronic low back pain.

My purpose, in this study, was to test the reflex-spasm model of chronic pain by comparing the levels of muscle activity in the lumbar paraspinal muscles of subjects with and without chronic low back pain (CLBP). Each group, the CLBP group and the nonpain (NP) group, comprised 11 subjects who were matched by age and sex. I used surface electrodes to record integrated electromyographic (IEMG) activity from each side of the low back. All subjects performed three experimental tasks and a reference (normalizing) task. The three experimental tasks were quiet sitting, standing, and sitting during a repetitive unilateral upper extremity task (active sitting). The CLBP and NP groups showed no significant difference for any of the three experimental tasks. For both groups, the active sitting IEMG levels were significantly higher than the quiet sitting and standing IEMG levels. The quiet sitting and standing IEMG levels were not significantly different from each other. The findings of similar levels of IEMG activity in both the CLBP and NP groups while they performed these tasks suggested that the reflex-spasm cycle was not present and, therefore, was not a cause of pain in the subjects with CLBP.